Ramazzoite, from the Monte Ramazzo Mine
Infrared spectrum of ramazzoite in the water region
1
Mineral
Sciences Department, Natural History Museum of Los Angeles County, 900
Exposition Boulevard, Los Angeles, CA 90007, USA
2
Division
of
Geological and Planetary Sciences, California Institute of Technology,
Pasadena,
CA 91125, USA
3 Dipartimento
per lo Studio del Territorio e delle
sue
Risorse, Università degli Studi di Genova, Corso Europa 26 - 16132
Genova,
Italy
4Dipartimento
di Scienze della Terra, Università di
Pisa,
Via S. Maria 53, I-56126 Pisa, Italy
5 via
XXV Aprile 28, I-16046 Mezzanego, Italy
6 via
Palmanova 67, I-20132 Milano, Italy
Ramazzoite (IMA2017-090), [Mg8Cu12(PO4)(CO3)4(OH)24(H2O)20][(H0.33SO4)3(H2O)36], is a new polyoxometalate mineral from the Monte Ramazzo mine, near Genova, Liguria, Italy. It occurs on
magnetite-rich matrix in association with chlorartinite, chrysotile,
dypingite,
goethite, lepidocrocite and nesquehonite, and
is
a late-stage, secondary mineral crystallizing from
low-temperature, aqueous solutions. Ramazzoite forms as simple cubes up
to about 0.15 mm on edge. The mineral is blue to greenish-blue with a
vitreous to
oily lustre and pale blue streak. Crystals are very brittle with
conchoidal
fracture, and a perfect
cleavage
on {100}. The Mohs’ hardness is 2½. The measured density is 1.98(1)
g·cm-3.
The mineral is soluble with mild effervescence in dilute HCl at room
temperature. Optically, ramazzoite is isotropic with n
= 1.491(1) (white light). Electron microprobe analyses gave the
empirical formula [(Mg8.00)(Cu8.00Mg3.78)(PO4)(CO3)4(OH)24(H2O)20]
[(H0.65S1.01O4)3(H2O)36],
based on 1 P apfu.
Ramazzoite
is cubic, P-43m, with
the unit cell parameters: a
= 13.3887(10) Å, V =
2400.0(5) Å3 and Z
= 1. The crystal structure,
refined to R1
= 0.064 for 803
observed reflections [I >
2σI], contains a novel [Mg8Cu12(PO4)(CO3)4(OH)24(H2O)20]5+
polyoxometalate cation.